The one with the locking ring or collar that has to be turned is the original NL series, before they modified the design. They work fine, but I found they confused many people. The concept is similar to the present day ones, in that you inserted the plug and then gave it a quarter-turn; then you had to rotate the locking collar to firmly lock it into place. The big user problem was they wouldn't go in fully and turn if the locking collar was already in the locked position (or even partially so), which could happen while being transported or stored. It really wasn't all that complicated, but inexperienced users like stage hands always seemed to be buffaloed by them. Changing to the slide-latch locking mechanism was the best thing that ever happened to that connector.
BTW, @Jim C -- you can change out just the outer shell of that old-style connector for a newer one without having to replace the inner (connector) part of the assembly. So no actual re-wiring. I changed out a bunch over time by salvaging the outer part from newer connectors that had failed.